The present invention relates to a semiconductor integrated circuit device and a manufacturing technique therefor. More specifically, the present invention relates to a technique effectively applicable to a FeRAM (Ferroelectric Random Access Memory).
A ferroelectric random access memory (FeRAM) is a nonvolatile memory using a binary characteristic of the polarization state of PZT (Pb(ZryTiz)O3) or the like which is a ferroelectric substance. A memory cell of this FeRAM consists of one memory cell selection MISFET and one information capacitor. A PZT film is used as the capacitive insulating film of the capacitor.
Since the ferroelectric substance such as a PZT film contains much oxygen liable to cause reaction, the characteristic of the ferroelectric substance tends to be degraded by various treatments conducted in manufacturing steps.
For example, Japanese Patent Laid-open No. 8-55850 and No. 10-321811 describe a technique for preventing a reaction with oxygen by forming a hydrogen barrier layer.
Japanese Patent Laid-open No. 10-163437 describes a technique for preventing the reaction of oxygen contained in a capacitive insulating film constituting a capacitive element by covering the upper surface of the capacitive element with a sacrificial protection film.
Japanese Patent Laid-open No. 11-135736 describes a technique for preventing the degradation of a ferroelectric substance and a high-dielectric-constant material due to a reduction atmosphere by covering an overall capacitive element with a hydrogen barrier film.
Inventors of the present invention have developed the capacitive element of an FeRAM. The polarization characteristic of this ferroelectric film is degraded by the presence of either H2 (hydrogen) or H2O (water).
One of the causes of the occurrence of either hydrogen or H2O is the presence of an interlayer insulating film. That is, in the formation of a silicon oxide film, a silicon nitride film or the like by a plasma CVD (Chemical Vapor Deposition) method, hydrogen or H2O is generated during the reaction of material gas. In addition, the hydrogen or H2O is contained in the silicon oxide film. Besides, if a silicon oxide film is formed by performing heat treatment for an SOG film, hydrogen or H2O is generated by this heat treatment.
On the other hand, in case of an FeRAM having a peripheral circuit or a logic circuit provided around a memory cell formation region, multilayer wirings are provided if the logic circuit becomes complex.
Since interlayer insulating films are formed between these plural wirings, respectively, it is becoming more important to take measures against hydrogen or H2O.
An object of the present invention is to provide a technique for preventing film quality of a ferroelectric film constituting a capacitive element from being degraded.
Another object of the present invention is to provide a technique for improving the film quality of the ferroelectric film and thereby for improving characteristics of a FeRAM memory cell.
The above and other objects and novel features of the present invention will become apparent from description of the present specification and accompanying drawings.
Of inventions disclosed by the present application, the outline of representative ones will be briefly described as follows.
(1) A semiconductor integrated circuit device according to the present invention is a semiconductor integrated circuit device having an information transfer MISFET formed on a main surface of a semiconductor substrate, and a capacitor connected in series to said information transfer MISFET, wherein it has a first shielding film formed under a lower electrode and a second shielding film formed on the upper electrode of said capacitor.
According to means as described above, the first and second shielding films can prevent H2 or H2O from entering an upper or lower portions of the capacitor and prevent the characteristics of a high-dielectric-constant material or ferroelectric material (capacitive insulating film) from being degraded in the capacitor. In addition, the first and second shielding films can reduce diffusion of the components, e.g., lead included in the capacitive insulating film. The first and second shielding films may be made of lead compounds. Also, the capacitive insulating film may be made of a lead compound. If a lead composition ratio of each of the first and second shielding films is set higher than that of the capacitive insulating film, then lead diffused from the capacitive insulating film can be compensated by lead included in the first and second shielding films. Thereby, it is possible to prevent the characteristics of the capacitive insulating film from being degraded. The lead compound is exemplified by PZT (Pbx(ZryTiz)O3) or the like. In addition, if said upper or lower electrode is covered with the first and second shielding films, for example, by forming a side wall film on the side wall of the upper or lower electrode, or the like, then the present invention becomes more effective.
(2) A semiconductor integrated circuit device according to the present invention is a semiconductor integrated circuit device having an information transfer MISFET formed on a main surface of a semiconductor substrate, and a capacitor connected in series to the information transfer MISFET, wherein it has a shielding film formed under the lower electrode of said capacitor.
According to means as described above, the shielding film can prevent H2 or H2O from entering the lower portion of the capacitor and prevent the characteristics of the high-dielectric-constant material or ferroelectric material (capacitive insulating film) from being degraded in the capacitor. In addition, the shielding film can reduce diffusion of the components, e.g., lead included in the capacitive insulating film. Further, it is possible to improve the crystallinity of the capacitive insulating film on the shielding film. Since the insulating film under a region in which the capacitor is formed contains hydrogen by hydrogen annealing treatment, in particular, it is possible to prevent entry of the hydrogen. This shielding film may be made of a lead compound. Also, the capacitive insulating film may be made of a lead compound. If the lead composition ratio of the shielding film is set higher than that of the capacitive insulating film, lead diffused from the capacitive insulating film can be compensated by lead included in the shielding film. Therefore, it is possible to prevent the characteristics of the capacitive insulating film from being degraded. The lead compound is exemplified by PZT (Pbx(ZryTi2)O3) or the like.
(3) A semiconductor integrated circuit device according to the present invention is a semiconductor integrated circuit device having an information transfer MISFET formed on a main surface of a semiconductor substrate, and a capacitor connected in series to the information transfer MISFET, wherein is has an interlayer insulating film formed on the information transfer MISFET and the capacitor, the interlayer insulating film which has a barrier layer made of a high-dielectric-constant material or a ferroelectric material.
According to means as described above, the barrier layer can prevent H2 or H2O included in the interlayer insulating film from entering the capacitor and prevent the high-dielectric-constant material or ferroelectric material (capacitive insulating film) from being degraded in the capacitor. This barrier layer may be made of a lead compound. The lead compound is exemplified by PZT (Pbx(ZryTi2)O3) or the like. This barrier layer may be amorphous. The barrier layer may be formed so as to be put between the first and second insulating films. Also, in the case where a plug is formed in the interlayer insulating film, the bottom and side portions of the plug may be covered with a conductive film having a barrier property such as a TiN film or the like. Further, the barrier layer may be formed in all the interlayer insulating films between multi-layer wirings. In addition, the barrier layer may be formed in a passivation film formed on the uppermost wiring. Besides, the barrier layer may be formed only in the memory cell formation region without being formed in the peripheral circuit region.
(4) A manufacturing method of a semiconductor integrated circuit device according to the present invention comprises the steps of: forming an information transfer MISFET formed on a main surface of a semiconductor substrate; forming an insulating film on said MISFET; and sequentially depositing a shielding film, a first conductive film, a capacitive insulating film made of a ferroelectric material, and a second conductive film on said insulating film, and patterning these films, and thereby forming, on the shielding film, a capacitor constituted by a lower electrode made of the first conductive film, a capacitive insulating film, and an upper electrode made of the second conductive film.
According to means as described above, it is possible to manufacture a semiconductor integrated circuit device capable of preventing the characteristics of the high-dielectric-constant material or ferroelectric material (capacitive insulating film) from being degraded in the capacitor. In the case where the insulating film contains hydrogen by hydrogen annealing treatment, in particular, this hydrogen can be prevented from entering the capacitive insulating film. Also, if said insulating film is formed by a plasma CVD method or by performing heat treatment for an SOG film, it is possible to prevent entry of hydrogen or H2O generated by the treatment. Further, a shielding film may be formed even on the upper electrode. This shielding film may be made of a lead compound. The lead compound is exemplified by PZT (Pbx(ZryTiz)O3) or the like.
(5) A manufacturing method of a semiconductor integrated circuit device according to the present invention comprises the steps of: forming an information transfer MISFET and a capacitor which are formed on a main surface of a semiconductor substrate; sequentially depositing an insulating film, a barrier layer made of a high-dielectric-constant material or ferroelectric material, and a second conductive film, on the information transfer MISFET and the capacitor, and thereby forming an interlayer insulating film.
According to means as described above, it is possible to manufacture a semiconductor integrated circuit device capable of preventing the characteristics of the high-dielectric-constant material or ferroelectric material (capacitive insulating film) from being degraded in the capacitor. In the case where the insulating film is formed by a plasma CVD method or by performing heat treatment for an SOG film, in particular, the barrier layer can prevent hydrogen or H2O generated by the treatment from entering the capacitor. This barrier layer may be made of a lead compound. The lead compound is exemplified by PZT (Pbx(ZryTi2)O3) or the like.